Transistorized ignition circuit



Sept. l2, 1,967 P. scHlFF 3,340,861

- TRANSISTORIZED IGNITION CIRCUIT Filed Sept. 16, 1964 United StatesPatent O 3,340,861 'IRANSISTORIZED IGNITION CIRCUIT Peter Schilf,Somerville, NJ., assignor to Radio Corporation of America, a corporationof Delaware Filed Sept. 16, 1964, Ser. No. 396,834 12 Claims. (Cl. 12S-148) the primary winding of the ignition coil to a safe value,

especially under stall or idle conditions. This ballast -resistance maybe built into the coil or may be in the form of a separate ballastresistor. During starting, when a good spark is particularly desirable,the battery voltage available for ignition may be substantially reduceddue to the large amount of current required by the starting motor, andthis voltage is reduced still further by the previously mentionedballast resistance. This reduction in voltage results in a proportionaldecrease in the primary winding current. Since the spark energy is afunction of the second power of primary winding current value, theenergy per spark is greatly reduced by a small reduction in primarywinding current. Switch means may be provided to short -circuit theballast resistor during starting to provide higher ignition coil currentat that time. During high speed operation, when the ignition points areclosed only for a short time, the ballast resistance may so lengthen thetime constant of the circuit including the ignition coil and, therefore,the time required for sucient current to build up in the coil, thatsuicient energy may not be stored in the primary `winding of theignition coil, during the short time that the points are closed betweensparks, to insure good ignition. Therefore, the provision of a seriesresistance in the ignition circuit of an internal combustion engine,while providing necessary current limiting during stall and low speedoperation, is detrimental to starting and high speed operation ofinternal combustion engines using spark ignition.

Furthermore, in many ignition systems, the ignition points are burned orpitted during operation thereof due to the making and breaking of highcurrents by the ignition points and due to the high voltage inducedacross them (called inductive kick back) as the result of the highlyinductive ignition circuit. In such circuits, the ignition points mustbe adjusted or replaced periodically. Circuits including vacuum tubesand transistors are known in which ignition points are unnecessary or inwhich the current flowing through the points is minimized and in whichthe inductance of the ignition coil is isolated from the ignitionpoints, whereby ignition troubles due to point burning and pitting areavoided. In many of these electronic ignition systems, a transistor orvacuum tube acts as a switch in the series circuit including the primarywinding of the ignition coil. In such circuits using transistors,excessive current ilow in the ignition coil during stall and slow speedoperation of the engine may cause the Voltage induced across the seriesswitching transistor, when the ignition points are subsequently opened,to ybuild up to a point where the inductive kick back may cause failureof the switching transistor. The transistor may be protected Ibylimiting the effect of this kick back -by connecting a Zener diode or acapacitor across the primary winding of the coil, or across theswitching transistor itself. By limiting the primary winding current,the protective components may be reduced to a minimum size and theoverall eciency of the circuit may be increased.

It is an object of this invention to provide an improved transistorizedinternal combustion engine ignition system.

It is a further object of this invention to provide an improvedtransistorized ignition system in which ballast resistance is notrequired. I

Another object of this invention is to provide an improvedtransistorized ignition system for internal combustion engines whichreduces the time in which increased current through the ignition Icoilis attained compared to that required in such ignition systems knownheretofore.

An additional object of this invention is to provide an improvedtransistorized ignition system presenting improved high speed engineperformance coupled with good starting characteristics.

In accordance with this invention, the switching transistor of atr-ansistorized ignition system is operated at saturation to initiatecurrent flow therethrough and through the ignition coil, and thiscurrent ow is limited by suitable means to a desired maximum valueregardless of the voltage of the supply source (above a certain lowvalue thereof) and independently of the time the ignition points areclosed and the switching transistor is conductive.

The novel features of this invention, both as to its organization andmethod of operation, as well as additional objects and -advantagesthereof, will be understood more readily from the following description,when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram of an internal combustion engine ignition circuitaccording to this invention in which the battery positive terminal andone of the ignition points are grounded;

FIG. 2 is a circuit diagram of another embodiment of this invention inwhich the battery negative terminal and one of the ignition points aregrounded;

FIG. 3 is a circuit diagram of a further embodiment in :accordance withthis invention.

In FIG. 1, the negative terminal 10 of a potential source as indicated,such as the battery of an automobile, is connected to the emitter of anNPN switching transistor 12 through a small emitter resistor 14. Thecollector of the switching transistor 12 is connected to the otherterminal 16 of the potential source, which may be grounded, through theprimary winding of an ignition transformer'or coil 18. A voltagelimiting Zener diode 20 may be connected between the emitter and thecollector of the switching transistor 12 for a purpose to be explained.The secondary or high voltage winding of the ignition transformer orcoil 18 is connected between the terminal 16 and the distributor of amulti-cylinder internal combustion engine. The negative terminal 10 ofthe potential source is also connected to the terminal 16 through aresistor 22, and through the emitter to collector path of an NPN drivertransistor 24 and a further resistor 26, all in series. The emitter ofthe driver transistor 24 is also connected to the base of the switchingtransistor 12. A fourth resistor 28 is connected `between the terminal10 and the base of the transistor 24. A fth resistor 30 and a switch 32,which represents the engine ignition points, are connected in seriesbetween the base of the driver transistor 24 and the terminal 16. Aplurality of diodes 34 in series are connected in parallel with theresistor 28. The diodes 34 are poled to be conductive with respect tothe potential source, i.e., cathode to anode, and final cathode directlyto the-negative terminal 10. In the normal operation of the internalcombustion engine of which the circuit described above is the ignitioncircuit, the normally closed points 32 are opened, when an ignitionsparkis needed, by a cam (not shown) that is rotated 'by the engine. Thecircuit of FIG. 1 is adapted to be used with an engine Where thepositive terminal of the battery is grounded and where it isadvantageous to ground one of the ignition points.

VConsidering the operation of the circuit of FIG. l, when the points 32are opened, no voltage is applied to the base of the driver transistor24 with respect to the emitter thereof, whereby substantially no currentflows between the collector and the emitter of the driving transistor24, and no current tlows into the base of the switching transistor 12.The switching transistor 12 is opened circuited and substantially nocurrent ows through the primary winding of the coil 18. When the points32 are in contact or closed, a positive voltage is applied to the baseof the NPN driving transistor 24 with respect to its emitter throu-ghresistor 30. The voltage drop across the resistor 28 is limited by theforward conduction voltage drop of the diodes 34 in series. By suitablychoosing the number and types of these diodes 34, the voltage appliedthereby between the negative side of the battery and the base of thedriving transistor 24 may be predetermined. The driving transistor 24,which acts as a current ampliier, becomes conductive and current flowsthrough the resistors 22 and 26. Due to the connection of the emitter ofthe driving transistor 24 and the base of the switching transistor 12, avoltage which is positive with respect to the emitter of the switchingtransistor 12 appears on the base thereof. The diodes 34, due to thedescribed circuit, 'are effectively connected from the base of thetransistor 12 to the terminal 10. The switching transistor 12immediately becomes fully conductive or saturated and current builds upin the primary winding of the coil 18 and in the resistor 14 during aperiod of time depending on the time constant of the circuit includingthe primary winding of the ignition coil 18. As the current builds up inthe emitter resistor 14, the voltage drop across this resistor builds upat the same rate. This voltage is in a direction to reduce the positivevoltage on the base of the `switching transistor 12 with respect to itsemitter. This voltage builds up to the point where the voltage betweenthe base and emitter of the switching transistor 12 is at some valuesuch that the switching transistor 12 operates below saturation thereofand at a safe operational value. The switching transistor current islimited to the safe operational value by the voltage developed in itsemitter to base circuit. As pointed out above, the switchingr transistoroperates in saturation during the early part of the current build-upperiod of the ignition coil. Therefore, current builds up to thislimited value as fast as the time constant of the ignition coil primarywinding circuit permits. The resistance value of the emitter resistor 14is so chosen that the voltage between the emitter and the base of thetransistor 12 is equal to about the threshold voltage of the baseemitter path of the transistor at the maximum desired current throughthe transistor 12. The resistor 14 which, in one particular embodimentof this invention, has a value of one-tenth to two-tenths of an ohm doesnot act as a ballast resistor since the voltage drop thereacross atmaximum current flow may be only 1 to 2 volts. The current through theswitching transistor 12 is limited by the operation of the circuitdescribed to nearly the same value for widely varying supply voltages(from about three and a half volts to about 14 volts) and for widelyvarying periods of ignition point closure, whereby no current limitingresistance need be built into the ignition coil and no ballast resistoror any switch for disconnecting a ballast resistor from the ignitionsystem is necessary, and yet this described circuit provi-des quickbuild-up of current ow to a maximum value which provides a hot ignitionspark when the ignition coil circuit is broken. Therefore, the describedignition circuit causes operatori in an improved manner of engines ofwhich it is a part, during starting, stall, idling, and high speedoperation thereof, and independently of available battery voltage,within a wide range, as compared to engines having known ignitionsystems.

The Zener diode 20 across the collector and emitter of the switchingtransistor 12 protects the transistor 12 from the high voltage kick backinduced in the primary winding of the ignition coil 18 during operationof the above dcscribed circuit by providing a shunt between the emitterand collector for kick back voltages.

FIG. 2 shows a circuit of an embodiment of this invention in whichadditional current limiting is provided and in which the negativeterminal of the supply source (not shown) and one of the ignition pointsmay be grounded. In this gure, the positive terminal 36 of the supplysource is connected to the collector of an NPN switching transistor 38through the primary winding of an ignition coil 40. A capacitor 42 maybe connected across this primary Winding for a purpose to be disclosed.One terminal of the secondary winding of the ignition coil 40 isconnected to the positive terminal 36, and the other terminal of thesecondary winding may go to the distributor (not shown) of amulti-cylinder internal combustion engine. The emitter of the switchingtransistor 38 is connected to the other terminal 44 of the source, whichother terminal may be connected to ground, through a small emitterresistor 46, A pair of diodes 48 in series, shunted by a resistor 50,are connected between the base of the switching transistor 38 and theterminal 44. The diodes 48 are poled so that the low resistancedirection of current -flow therethrough is from the base of thetransistor 38 to the terminal 44. The emitter of a PNP drivingtransistor 52 is connected to the positive terminal 36 through a smallemitter resistor 54. The collector of the driving transistor 52 isconnected to the terminal 44 through the resistor 50. A diode 56 and aresistor 58 in parallel are connected between the positive terminal 36and the base of the driving transistor 52. The diode 56 is poled so thatits low resistance direction of current ow is from the terminal 36 tothe base of the driving transistor 52. The base of the drivingtransistor 52 is also connected to the terminal 44 through a resistor 60and a switch 62 which rrepresents the engine ignition points. Thesepoints 62, as noted above, are normally closed and are openedmomentarily by a cam (not shown) to produce an ignition spark.

The operation of FIG. 2 is as follows: When the ignition points 62 areopened, the emitter and base of the driving transistor 52 are at zeropotential with respect to each other, whereby the driving transistor 52is nonconductive and no current ows through the resistors 50 and 54. Thebase and the emitter of the switching transistor 38 are also at zeropotential with respect to each other and no current ows through theswitching transistor 38 0r through the primary winding of the ignitioncoil 40, which is in series therewith. When the ignition points 62 areclosed, current 4flows through the resistors 58 and 60 in series and thevoltage on the base of the driving transistor 52 becomes negative withrespect to the voltage on its emitter. The driving transistor 52conducts and current flows from the positive terminal 36 through theresistor 54, through the emitter to collector path of the drivingtransistor 52 and through the resistor 50 to the terminal 44. Thevoltage drop between the emitter and base of the driving transistor 52is limited to the voltage drop of the diode 56 in its forward direction,less the voltage drop developed `across the small emitter resistor 54.'Ihe effect of the voltage across the diode 56 and resistor 54 is tolimit the current through the driving transistor 52 to a value less thanthat at saturation thereof. The voltage across the resistor 50 isapplied across the diodes 48 in the forward direction, and also betweenthe base and emitter of the switching transistor 38 in series with theemitter resistor 46 in a direction to render the transistor 38conductive. The voltage developed across the resistor 50 is limited tothe drop across the diodes 48 in series in their forward direction, andthe voltage applied between the emitter and the base of the transistor38 is the voltage developed across the diodes 48 in series less thevoltage developed across the resistor 46 which may have a resistance of0.1 to 0.2 ohm. When no current is owing in the resistor 46, thisvoltage is sucient to drive the switching transistor 38 into saturation.Current builds up in the collector-to-emitter path of the switchingtransistor 38 and in the primary winding of the ignition coil 40 at arate determined by the time constant of the ignition coil circuit. Thevoltage across the resistor 46, which builds up at the same rate,opposes the Voltage across the diodes 48 in series, thereby limiting thecurrent through the switching transistor 38 to a value less than thesaturation value. The limited current flow through the collector of thetransistor 52 provides a substantially constant current in the parallelcircuit comprising the resistor 50 and the diodes 48. The Voltage dropacross the diodes 48 is more nearly constant than if the currenttherethrough were not so limited by operation of the circuit of thetransistor 52. Since the voltage across the diodes 48 is stabilized, themaximum current ow through the transistor 38, which depends on thedilerence of voltage developed across resistor 46 and the diodes 48 inseries is more nearly independent of the voltage of the source than ifthe transistor 52 had no current limiting function. The result is thatthe current through the primary of the coil 40 rises very quickly to asafe and suflicient operating value for high speed operation, and thecurrent is limited to a safe operative value for a wide range of supplyvoltages and periods of closure of the points ranging from stall to highspeed operation. A condenser 42 may be provided across the coil 40 tolimit the voltage developed across the transistor 38 by the inductivekick back when the points 62 are opened by the engine cam. By choice ofthe number and types of diodes 56 and 48 and the size of the resistors54 and 46, the limited Value of the current which ows through theignition coil 40 may be selected to provide a desired maximum currentthrough the transistor thereby to produce a good ignition spark .at allconditions of engine operation. The diodes 56 and 48 provide atemperature compensating elfect for their associated transistors in aknown manner. Therefore, if silicon transistors are used, it ispreferable to use silicon diodes, since the temperature resistancecharacteristics of the silicon diodes 48 `and of the silicon transistor38 are similar.

In the embodiment of FIG. 3, an ignition circuit is shown that requiresno driving transistor. The positive terminal 36 of a source (not shown)is connected through the primary winding of an ignition coil 40 andthrough the collector to emitter path of an NPN switching transistor 38and through a small emitter resistor 46 to the other terminal 44. Oneterminal of the secondary winding of the ignition coil 40 is connectedto this positive termin-al 36 and the other terminal of the secondarywinding is connected to the distributor (not shown). The positiveterminal 36 is also connected through the ignition points 66 and aresistor 64 and two diodes 48 in series to the other terminal 44. Thetwo diodes 48 are connected in their forward direction between the baseof transistor 38 and the other terminal 44. The base of the transistor38 is connected to a point between the diodes 48 and the resistor 64.

Operation of the circuit of FIG. 3 is like that of the circuit of FIG. 2described hereinabove. When the points 66 are opened, the Voltage on theemitter and the base of the transistor 38 is practically the samewhereby the transistor is substantially non-conductive. Upon closing thepoints 66, a voltage is applied to the base of the transistor 38 that ispositive with respect to its emitter, causing the transistor 38 tobecome saturated. This voltage on the base with respect to the emitteris limited by the voltage drop of the diodes 48 in their forwarddirection and is equal to the drop across these diodes 48 less thevoltage drop across the resistor 46. The current 'through the circuitincluding the coil primary winding and the transistor 38 rises at a ratedetermined by the time constant of the circuit including the coilprimary winding, -and the voltage across the'resistor 46 rises at thesame rate. The transistor 38 operates at saturation for the Alirst partof the period of conductivity thereof. The current continues to rise invalue to its maximum. The maximum current through the transistor 38 islimited by the voltage applied between the emitter and 'base thereof.This voltage is less than the xed drop across the series diodes 48 bythe voltage drop across the resistor 46. When the points 66 are closed,the current through the coil 40 rises quickly to a maximum value whichis determined by the voltage between the emitter and the base of thetransistor 38. Thus the ignition systern produces a hot spark andrequires no ballast resistance, -and yet operates in an improved mannerin a Wide range of speeds. The transistor 38 in FIG. 3 may be such thatkick back protection therefor is not necessary.

In each of FIGS. 2 and 3 the resistance Value of the emitter resistors46 and 54 are so chosen that the voltage across each emitter resistor atm-aximum desired current through th-e transistor to which it isconnected, plus the threshold voltage of the base-emitter path of saidtransistor, is equal to the forward threshold voltage of the diode, ordiodes in series, connected to the base of said transistor.

While three ignition circuits according to the present invention havebeen shown and described, it will undoubtedly be `apparent to thoseskilled in the art that variations thereof are possible within thespirit of this invention. For example, by reversing the voltages and theconnections of the diodes, PNP transistors may be substituted for theNPN transistors in the several figures and an NPN may be substituted forthe PNP transistor shown in FIG. 2. Other changes will, no doubt, alsosuggest themselves readily. Hence, it should be understood that theforegoing description is to be considered as illustrative and not in alimiting sense.

What is claimed is:

1. A transistor circuit comprising (a) a pair of terminals forconnection to a source of potential,

(b) a switching transistor having an emitter and a collector,

(c) an inductive load connected between one of said terminals and saidcollector,

(d) an emitter resistor connected between said emitter and the other ofsaid terminals,

(e) means to render said transistor alternately nonconductive andconductive, and

(f) means including said emitter resistor to cause said transistor toconduct in a saturated manner during the early part of 'current build upthrough the transistor and tolimit the maximum current ow therethroughto -a predetermined operating value.

2. A transistor circuit comprising (a) a pair of terminals forconnection to a source of potential,

(b) a switching transistor having an emitter, a collector and a baseelectrode,

(c) an inductive load connected between one of said terminals and saidcollector,

(d) an emitter resistor connected between said emitter and the other ofsaid terminals,

(e) at least one diode connected between said base and said emitterthrough said emitter resistor, said diode being poled in the currentconductive direction from said terminal connected to said collectorthrough the internal collector-to-base path of said transistor to theother terminal of said source, and

(f) means to render said transistor alternately conductive andnon-conductive, said diode and said emitter resistor acting to causeconduction saturation of said switching transistor during the early partof current buildup therethrough when conductive, and to limit themaximum current flow therethrough to a predetermined operating value.

3. A tra'nsistorized ignition system comprising (a) an ignition coilhaving primary and secondary windings,

(b) a pair of terminals for connection to a source of potential,

(c) a switching transistor having an emitter and a collector,

(d) an inductive load comprising said primary winding connected betweenone of said terminals and said collector,

(e) an emitter resistor connected between said emitter and the other ofsaid terminals,

() a pair of openable and closeable ignition points,

(g) means responsive to the opening and closing of said points to rendersaid transistor respectively non-conductive and conductive, and

(h) means including said emitter resistor to cause said transistor toconduct in a saturated manner during the early part of current build uptherethrough when said points are closed and to limit the maximumcurrent ow therethrough to a predetermined operating value.

4. A transistorized ignition system comprising (a) an ignition coilhaving primary and secondary windings,

(b) a pair of terminals for connection to a source of potential,

(c) a switching transistor having an emitter and a collector,

(d) a small emitter resistor connected between one of said terminals andsaid emitter,

(e) said primary winding of said coil being connected between saidcollector and the other of said terminals,

(f) a second transistor having main electrodes and a control electrode,said main electrodes being connected between said terminals,

(g) means including a pair of openable and closable ignition points torender said second transistor nonconductive and conductive respectivelyin response to opening and closing of said points,

(h) voltage limiting means connected between one of said main electrodesand said control electrode of said second transistor, and

(i) means responsive to the flow of current in said second transistor tocause said switching transistor to conduct, said voltage limiting meansand said emitter resistor acting to permit conduction of said switchingtransistor in a saturated manner during the early part of currentbuild-up therethrough and to limit the maximum current therethrough to apredetermined operating value.

5. A transistorized ignition system comprising (a) an ignition coilhaving primary and secondary windings,

(b) a pair of terminals for connection to a potential source,

(c) a switching transistor having an emitter, a -collector, and a baseelectrode,

(d) said primary winding being connected between said collector of saidtransistor and one of said terminals,

(e) an emitter resistor connected between said emitter and the other ofsaid terminals,

(f) voltage limiting means effectively connected between said base ofsaid switching transistor and said other terminal7 (g) a pair ofopenable and closable ignition points connected in a circuit betweensaid terminals, and

(h) means responsive to opening and closing of said points for renderingsaid switching transistor, alternately non-conductive and conductive,said voltage limiting means and said resistor acting to permitconduction of said switching transistor in a saturated manner during theearly part of current build-up therethrough and to limit the maximumcurrent therethrough to a predetermined operating value.

6. A transistorized ignition system comprising (a) a pair of terminalsfor connection to a source of potential,

(b) a switching transistor having an emitter, a collector and a baseelectrode,

(c) an ignition coil having primary and secondary windings, said primarywinding being connected between one of said terminals and saidcollector,

(d) an emitter resistor connected between said emitter and the other ofsaid terminals,

(e) at least one diode connected between said base and said emitterthrough said emitter resistor, said diode -being poled in currentconductive direction from said terminal connected to said collectorthrough the internal collector-to-base path of said transistor to theother of said terminals,

(f) a pair of openable and closable ignition points, and

(g) means responsive to the closing of said ignition points to apply acurrent to the base of said transistor to render it conductive, saiddiode and said emitter resistor acting to permit conduction of saidswitching transistor in a saturated manner during the early part ofcurrent build-up therethrough, and to limit the maximum current flowtherethrough to a predetermined operating value.

7. A transistorized ignition system comprising (a) a pair of terminalsfor connection to a source of potential,

(b) a switching transistor having an emitter, a collector, and a baseelectrode7 (c) an ignition coil having primary and secondary windings,said primary winding being connected between one of said terminals andsaid collector,

(d) a first emitter resistor connected between said emitter and theother of said terminals,

(e) at least one diode connected between said base and said emitterthrough said first emitter resistor, said diode being poled in currentconduction direction from said terminal connected to said collectorthrough the internal collector-to-base path of said transistor to theother of said terminals,

(f) a second transistor having an emitter, a collector and a base,

(g) a second emitter resistor and a collector resistor,

(h) said second transistor emitter being connected to said one terminalof said source through said second emitter resistor,

(i) said second transistor collector being connected to said otherterminal of said source through said collector resistor and said diodein parallel,

(j) an additional diode connected between said one terminal of saidsource and the base of said second transistor and poled in its currentconductive direction, with respect to said source,

(k) a pair of openable and closable ignition points, and

(l) means responsive to the closing of said ignition points to apply acurrent to the base of said second transistor to'cause it to conduct,said second diode `and said second emitter resistor acting to causelimite-d current ow through said collector resistor,

said limited current flow causing said switching transistor to conduct,said iirst diode and said rst emitter resistor acting to cause saidswitching transistor to begin to conduct in a saturated manner and tolimit the maximum current ow through said switching transistor to apredetermined maximum value. 8. A transistorized ignition systemcomprising (a) a circuit having (1) a pair of terminals for connectionto a current Supply, (2) an ignition coil including a primary winding,(3) a switching transistor having an emitter-tocollector path, and (4) asmall emitter resistor,

said emitter-to-collector path, said primary -winding and said resistorbeing connected in series between said pair of terminals, and saidemitter being connected to one terminal of said emitter resistor,

(b) openable and closable ignition points,

(c) circuit means including said points for rendering said switchingtransistor alternately non-conducting and conducting at saturation inresponse to opening and closing of said points, respectively, and

(d) means including said emitter resistor for limiting the maximumcurrent flow through said transistor to less than the saturation valuethereof.

9. A transistorized ignition system comprising (a) a circuit having (l)a pair of terminals for connection to a current Supply, (2) an ignitioncoil including a primary winding, (3) a switching transistor having anemitter-tocollector path, and (4) a small emitter resistor;

said emitter-to-collector path, said primary winding and said emitterresistor being connected in series between said pair of terminals, andsaid emitter being connected to one terminal of said emitter resistor,

(b) openable and closable ignition points,

(c) circuit means including said points for rendering said switchingtransistor alternately non-conductive and conductive at saturation inresponse to opening and closing of said points, and

(d) at least one diode effectively connected in its forward conductivepolarity from the base to the emitter of said transistor through saidemitter resistor, said diode and said emitter resistor acting to limitthe maximum current through said transistor to a value less than thesaturation value thereof.

10. A transistorized ignition system comprising (a) a pair of terminalsfor connection to a current source,

(b) a switching transistor having an emitter, a collector, and a baseelectrode,

(c) a iirst emitter resistor connected between a rst one of saidterminals and said emitter,

(d) an ignition transformer having a primary winding connected betweensaid collector and the other of said terminals,

(e) at least one diode connected between said base and said firstterminal poled for current conduction from said source,

(f) at least one other resistor,

(g) a pair of ignition points,

(h) one of said points being connected to said irst terminal,

(i) the other of said points being connected to said other terminalthrough said other resistor,

(j) an additional diode connected across said other resistor,

(k) a driving transistor having an emitter, a collector,

and a base,

(l) a second emitter resistor connected between aterminal of otherresistor and the emitter of said driving transistor, A

(m) the base of said driving transistor being connected to the otherterminal of said other resistor,

(n) said additional diode being poled for current conductiontherethrough from said source,

(o) a connection between said collector of said driving transistor andsaid base of said switching transistor, and

(p) a further resistor connected across Said first named diode.

11. A transistorized ignition system comprising (a) a pair of terminalsfor connection to a current source,

(b) a switching transistor having an emitter, collector,

and a base,

(c) an emitter resistor connected between a first one of said terminalsand said emitter,

(d) an ignition transformer having a primary winding connected betweensaid collector and the other terminal of said source,

(e) a resistor connected between said base and said first terminal,

(f) a driving transistor having main electrodes and a control electrode,

(g) a connection from one of said main electrodes to the base of saidswitching transistor,

(h) a resistive connection from the other of said main electrodes tosaid other terminal of said source, (i) a resistor connected from saidrst terminal to said control electrode,

(j) at least one diode connected across said last named resistor, saiddiode being poled for current conduction from said source, and

(k) a pair of ignition points,

(l) one of said points being connected to said other source terminal andthe other of said points being connected to said control electrode.

12. A transistorized ignition system comprising (a) a pair of terminalsfor connection to a source of current,

(b) a switching transistor having an emitter, a collector and a base,

(c) an ignition coil having a primary winding connected between saidcollector and one of said terminals,

(d) a small emitter resistor,

(e) said emitter being connected through said small emitter resistor tothe other terminal of said source,

(f) a pair of ignition points,

(g) an additional resistor connected through said pair of ignitionpoints to said one terminal,

(h) at least one diode,

(i) said last named resistor being connected through said diode to theother terminal of said source, and

(j) -a connection between the junction of said last named resistor andsaid diode to said base, said diode being poled for current conductionbetween said terminals with respect to said source.

References Cited UNITED STATES PATENTS 3,016,476 1/1962 Bataille 123-1483,016,477 1/ 1962 Naborowski 123-148 3,219,876 11/1965 Bays et al.123-148 3,249,808 5/1966 Short 123-148 3,259,798 7/1966 Yonge 123-1483,288,125 11/1966 Guyton et al. 123-148 LAURENCE M. GooDRIDGE, PrimaryExaminer.

1. A TRANSISTOR CIRCUIT COMPRISING (A) A PAIR OF TERMINALS FORCONNECTION TO A SOURCE OF POTENTIAL, (B) A SWITCHING TRANSISTOR HAVINGAN EMITTER AND A COLLECTOR, (C) AN INDUCTIVE LOAD CONNECTED BETWEEN ONEOF SAID TERMINALS AND SAID COLLECTOR, (D) AN EMITTER RESISTOR CONNECTEDBETWEEN SAID EMITTER AND THE OTHER OF SAID TERMINALS, (E) MEANS TORENDER SAID TRANSISTOR ALTERNATELY NONCONDUCTIVE AND CONDUCTIVE, AND (F)MEANS INCLUDING SAID EMITTER RESISTOR TO CAUSE SAID TRANSISTOR TOCONDUCT IN A SATURATED MANNER DURING THE EARLY PART OF CURRENT BUILD UPTHROUGH THE TRANSISTOR AND TO LIMIT THE MAXIMUM CURRENT FLOWTHERETHROUGH TO A PREDETERMINED OPERATING VALUE.